A comprehensive review on geotechnical properties of alkali activated binder treated expansive soil

Geopolymer based soil stabilization is an emerging research field as shown by recent research studies which indicate strong potential of their wide use for sustainable ground treatment. This paper comprehensively reviews the literature on expansive soil stabilization using alkali activated binders, focusing on the stabilization mech-anism and geotechnical characteristics of treated soil inclusive of mechanical strength and durability charac-teristics. The stabilization mechanism is governed by the cation exchange process and the geopolymer/hydration products formation. The reported highest unconfined compressive strength (UCS) and California bearing ratio (CBR) of the geopolymer treated expansive soil cured at room temperature are 15 MPa and 81%, respectively and these values satisfy the strength criteria of most of the standards used for road base materials. The findings of the review revealed that incorporation of precursors in the range of 15-20%, alkaline molarities between 5 and 10 M, along with strong alkalis (NaOH or KOH), Ca rich additives, and discrete fibers could enhance the stabili-zation performance with respect to strength, swell, and durability. Alkaline activation treatment is expensive compared to the conventional Portland cement based stabilization methods, and yet the cost can be significantly reduced by employing cost effective silicates for alkaline activation. Overall, alkali activated binders (AAB) can be sustainable stabilizers to treat expansive soils for satisfactory geotechnical performance (compaction, strength and durability), however, as recommended in this review, further research should be advanced to realize the utmost viability of this promising approach in successful field application.